The invention relates to a centrifuge comprising a centrifugal drum, an inflow tube leading into the centrifugal drum for feeding a centrifugal material into the centrifugal drum, and a device for cooling the centrifugal drum. The invention also relates to a method for operating a centrifuge according to the invention.
A centrifuge-of the above-mentioned type is known from German Patent Document DE OS 26 31 110. This document shows a centrifuge with a cylindrical solid-wall centrifugal drum whose shell can be continuously cooled by an insert arranged in the solid-material space by a circulating cooling medium. The insert is supported at several points in the drum shell and is guided in a sealing manner with respect to the separation space of the drum.
Although this cooling system is operable, a, problem arises with respect to the constructive expenditures required for achieving a cooling of the centrifugal drum. The expenditures excessively increase the costs for the manufacturing of the centrifuge particularly at lower cooling requirements.
German Patent Document DE PS 24 23 319 shows a centrifuge with a cylindrical solid-wall centrifugal drum whose shell can be continuously cooled by a circulating first cooling medium. The cooling medium leaves the drum shell at a radially exterior point and is thrown against a shell which is fixed to the frame and surrounds the drum. The shell fixed to the frame, in turn, can be additionally continuously cooled by a second cooling medium. This cooling system has also been successful but also excessively increases the costs for the manufacturing of the centrifuge in the case of lower cooling requirements.
Based on this state of the art, the invention aims at providing a centrifuge and a method for operating the centrifuge by means of which a cooling of the centrifuge can be implemented at low constructive expenditures.
In particular, the cooling should also be usable in the case of centrifuges with an automatic valve mechanism.
The invention achieves this goal. Accordingly, the cooling device includes and uses an outlet valve mechanism of the centrifugal drum which can be operated by a control fluid. The control fluid is cooled such that it acts as a cooling medium. The invention therefore surprisingly uses the valve mechanism of the centrifugal drum also as a cooling device. A separate cooling device is no longer required.
A cooling effect can particularly advantageously be achieved in that cooled sterile air is used as a control fluid. The cooling device, which includes control fluid connections, control fluid paths, an outlet valve mechanism and bores or passages, enables cooled control fluid to pass through the valve mechanism to cool the drum and its collected contents. During the centrifuging operation of the centrifuge, the valve mechanism is acted upon by a first sterile-air flow-through rate and, during an opening of a piston slide valve or control valve mechanism, is acted upon by a second sterile-air flow-through rate which is larger than the first flow-through rate. The first flow-through rate achieves a first cooling effect but does not yet displace the piston slide valve. On the contrary, this displacing is not implemented before the second flow-through rate.
Particularly preferably, sterile air is used as the control fluid because it is reasonable in price and can be handled in a particularly uncomplicated manner. As an alternative, other gaseous media can also be selected.
From German Patent Document DE 28 22 478, a centrifuge is known which comprises a centrifugal drum which has a piston slide valve to which a closing chamber is assigned which, by way of ducts in a spindle, is connected with a hydraulic system. The inflow of the product takes place from above by a central inflow tube. The spindle is situated on the underside of the centrifugal drum. This construction has been successful but reaches its limit when, for reasons of hygiene, the product range is to be situated separately from the driving range of the centrifuge and the control elements of the drive as well as the control elements of the control fluid supply outside the drum (valves, etc.).
This is the start of a further idea of the invention of assigning the feeding duct for the control fluid directly to the inflow tube for the centrifugal material. Because the control fluid feed line and the centrifugal material feed line are thus jointly guided into the centrifugal drum and preferably also extend directly side-by-side, a constructively separate feeding of the control fluid can be avoided.
The invention is particularly suitable for a centrifuge, in the case of which the centrifugal drum hangs on a centrifuge frame, the inflow tube for the centrifugal material and the feeding duct for the control fluid extending jointly from above into the centrifugal drum. In the case of centrifuges with hanging centrifugal drums, a separate feeding of the control fluid from below into the drum is not practical because it may be necessary to collect the solids separated during the separation process below the drum in a sterile vessel. This is clearly simplified by feeding the control liquid xe2x80x9cfrom abovexe2x80x9d.
According to a particularly preferred embodiment of the invention, a double wall is constructed on the inflow tube. The interior tube, for example, is used for feeding the centrifugal material and the conically exterior tube section is used as a feeding device for the control fluid. A double-walled tube is particularly space-saving. In addition, the interior inflow tube for the centrifugal material is cooled in the simplest manner by the fluid in the exterior tube section. Another advantage of this solution is the fact that a separate control air feeding device in the manner of a spindle is avoided.
Preferably, the control air supply also has the purpose of actuating a displaceable piston slide valve for opening and closing solid-matter removal openings in the centrifugal drum. In this case, an opening chamber and a closing chamber adjoin the piston slide valve. By the pressurization by the control fluid, the piston slide valve is moved, in which case it is also possible to hold the piston slide valve in a spring-tensioned manner in one of its working positions and to move it into the respective other working position by the pressure buildup in the corresponding control chamber.
Particularly preferably, according to another variant of the invention, the control and cooling medium is guided through an outlet opening in the drum wall into a solid-matter collecting container in order to cool the collected solids as well as preferably also the rotating drum itself, on which frictional heat is generated by the rotation of the drum. In this case, the control pressure can be selected such that the corresponding working position is maintained despite the xe2x80x9cleakagexe2x80x9d through the outlet opening.
The opening in the drum wall can also be used for draining a cleaning medium guided into the control fluid paths of the centrifuge.
Summarizing, the invention also implements a space-saving automatic valve mechanism which can also be used for the cooling.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.